Radiator apparatus for underwater sound generators



June 28, 1966 H. E. SAWYER 3,257,988

RADIATOR APPARATUS FOR UNDERWATER SOUND GENERATORS Filed Feb. 12, 1964 5 Sheets-Sheet 1 Harold E.Suwyer, lnv. deceased, Esther T. Sawyer, Administrutrix INVENTOR.

AH rney June 28, 1966 H. E. SAWYER 3,257,988

RADIATOR APPARATUS FOR UNDERWATER SOUND GENERATORS Filed Feb. 12, 1964 5 Sheets-Sheet 2 Fig.2

, Harold E. Sawyer, lnv. deceased, Esrher T. Sawyer, Administrcnrix INVENTOR.

Attorney June 28, 1966 H. E. SAWYER 3,257,988

RADIATOR APPARATUS FOR UNDERWATER SOUND GENERATORS Filed Feb. 12, 1964 3 Sheets-Sheet 3 Fig.4

Harold E. Sawyer, Inv. deceased, Esther T. Sawyer, Adminisirutrix INVENTOR.

Attorney United States Patent RADIATOR APPARATUS FOR UNDERWATER SOUND GENERATORS Harold E. Sawyer, deceased, late of Falmouth, Mass., by Esther T. Sawyer, administratrix, Harwich Port, Mass., assignor to the United States of America as represented by the Secretary of the Navy Filed Feb. 12, 1964, Ser. No. 344,512 5 Claims. (Cl. 11627) The present invention relates generally to apparatus for generating high intensity pressure pulses in a fluid medium and, more particularly, to a radiating device for use with mechanical impact sound sources.

Some of the desirable characteristics of sound pulses for underwater transmission, as is well known, include a shock wave front, high peak pressure, persistence of the peak pressure for a significant time and a clean decay. Although explosive devices develop peak pressures of extremely high magnitude, these pulses begin to decay immediately and are followed by undesirable secondary pulses. Because of their spiked configuration, explosive pulses experience relatively large scattering and absorption losses.

Pulses produced by plane impact-energized devices, for the most part, possess the characteristics enumerated above and, consequently, sound generators of this classification should find useful application in systems for study ing'the thickness of reflecting targets and bottom reflection conditions.

In applicants US. Patent No. 3,053,220, issued September 11, 1962, there is disclosed an impact-energized sound source capable of producing relatively high intensity pulses of short duration wherein the driving energy is derived from expansion of compressed, helical springs. In order to prevent deformation of the radiating piston and insure maximum efliciency, the impact rod which strikes the piston is designed with a mass equivalent to the sum of the piston mass and the effective mass due to radiation reaction of the piston. Also, the impact takes place in an evacuated chamber in order to reduce losses in compressing any gas between the impacting faces and to shorten the pulse so that higher pressure is possible for the same total energy. The contacting surfaces of the piston and impact rod, which are of equal area, are polished and kept parallel to insure even transfer and distribution of energy over the entire piston area.

If the impact force isa sound generator of the type shown in the above patent is not distributed uniformly over the total area of the piston, bending moments are up in the radiating surface. Accompanying these moments are surface deflections which introduce additional degrees of freedom into'the vibrating system, destroying the uniformity of velocity of all the points of the radiating surface and creating phase conditions which degrade the pulse shape.

It is accordingly a primary object of the present invention to provide a radiating assembly for use with a -mechanical impact sound source which is capable of developing extremely high intensity sound pulses.

It is a further object of the present invention to provide a radiating assembly for a sound generator which permits the intensity of the sound pulses to be changed.

A still further'object of the present invention is to provide a radiator assembly for a mechanical sound source wherein the radiating surface is maintained flat and in its proper attitude during its displacement cycle.

Patented June 28, 1966 A yet still further object of the present invention is to provide an arrangement for supporting a radiating surface that is impacted by a slug travelling at a high velocity, which arrangement maintains the radiating surface in its proper shape and orientation throughout its period of displacement.

A yet still further object of the present invention is to provide an arrangement for supporting the impacted piston which utilizes liquid springs to insure the proper positioning of the piston at the start of each displacement and maintains the piston surface coplanar during its displacement cycle. I

Since the apparatus of the present invention is intended to operate at a very high peak pressure in the vicinity, for

example, of 1.5 X 10 dynes/cm. at the piston-fluid interface, a level far higher than that of the device shown in the above patent, the radiating piston has a mass considerably greater than that of its counterpart and travels at a correspondingly higher velocity. Because of this, the radiating piston of the present invention cannot be supported by means of the relatively simple ring spring shown in the above patent. Rather, its increased mass, velocity and displacement require it to be supported at a multiplicity of internal points, as well as around its complete periphery, to avoid the deformation and disorientation problems previously discussed. In order to provide the requisite support for the radiating surface, the present inventionutilizes two comple-' mentary mechanisms. plicity of fluid springs fastened at distributed points over The first, which involves a multithe complete radiating surface of the piston, insures the 'coplanar condition of the inner radiating surface throughout its displacement cycle.

tor to divide off the enclosed space on the impact side of the piston which is evacuated from the space onthe radiating side which is filled with a fluid.

The main housing of the radiating assembly is closed off at one end by the piston and a cooperating annular bellows and at an opposite end by a window transparent to acoustic energy. The main body of the housing is 45.

completely filled with a noncorrosive fluid having an acoustic impedance near that of the fluid medium in which the apparatus is to be used. By utilizing fluid springs in the supporting arrangement and by designing these springs with small ports which permit a two-way flow of the fluid into andout of the springs, the internal pressure of all of the various springs can be equalized at their common initial position. Thus, each .spring is properly conditioned to absorb its percentage of the total impact energy. By disposing the springs in a grid arr'angement, the required structural strength is achieved with only an extremely small percentage of the total available cross-sectional area of the piston covered. Hence, the structure supporting the piston interferes to a minimum extent with the radiation of the acoustic energy from the piston face, which energy, of course, must propagate through the main body of the housing and through the acoustic window before reaching the surrounding fluid medium.

The fluid springs, it will be seen, are designed so that that portion of the impact energy to be absorbed by the springs is utilized to compress the spring fluid itself.

This technique provides a spring structure with the neoessary stiffness, having physical dimensions consistent with the space limitations on the radiating side of the piston. Only about 4% of total energy goes to the spring system. The rest goes out into the fluid medium as an acoustic pulse.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:

FIG. 1 illustrates the complete radiator assembly;

FIG. 2 shows the grid arrangement for supporting the various fluid springs;

FIG. 3 shows the construction of a typical fluid spring in its standby position; and

FIG. 4 shows a rim portion of one of the cones in the horn mouth section and the recess cut therein.

Referring now to FIG. 1 of the drawings, the complete radiating assembly without the drive is seen to consist of three interconnected subassemblies, namely, a throat section 1, a grid section 2 and a horn mouth section 3. Throat section 1 has an annular bellows or sealing ring 4 secured to its outer flanged portion 5. Closing off one end of this throat section is a radiating piston 6 having a projecting rim flange 7 which is secured to the innermost rim 8 of bellows 4. It will be seen from an examination of this section that the diameter of piston 6 at its radiating side precisely matches that of the cylindrical portion 9 of this section. Thus, piston 6 is capable of movement to the right, as seen in this figure, when impacted by a slug, not shown, hitting its striking surface 10, cylindrical portion 9 acting as a piston cylinder during this displacement of piston 6.

Secured to the radiating surface 11 of piston 6 are a multiplicity of fluid springs 12, 13, 14, etc., which in this particular embodiment are arranged in three concentric circles. These fluid springs are supported at one end by piston 6 and at an opposite end by grid section 2 in a manner which is, perhaps, best shown in FIG. 2.

Referring now to FIG. 2, it will be seen that grid section 2 consists of a multiplicity of tubular elements 15, 16, 17, etc., arranged in a concentric circular pattern matching that of the fluid springs. The individual tubular elements are interconnected by a network'of thin webs 18, 19, 20, for example, and the whole grid pattern is supported within its casing 21 by radial members, such as 22, 23, etc. It will be appreciated that for each fluid spring 12, 13, 14 there is a corresponding tubular element 15, 16, 17.

The construction of the fluid springs and their manner of operation can perhaps best be comprehended by referring now to FIG. 3 which shows the details of a typical spring in its normal or uncompressed conditions. Each spring, it will be seen, includes a piston member 30 made of tubular design so as to possess high column strength with a minimum cross section. One end 31 of piston 30 is threaded into and thereby secured to the radiating surface 11 of piston 6. Piston 30 has an enlarged diameter portion 32 at a location intermediate its length which, as will be seen hereinafter, acts during the terminal portion of each piston displacement to compress a fluid 3-3 accommodated within the spring assembly. 'Each s-p-ring also has an inner sleeve 34 which is accommodated and effectively locked to the tubular element 15, one of the members of the grid network. This inner sleeve is threaded at opposite ends 36 and 37 which extend beyond tubular element 15. An outer sleeve 38 is threaded at one end 3-9 to mate with threaded portion 36 of inner sleeve 34. Outer sleeve 38 is also threaded at its other end 40 so as to accommodate a tapered nosepiece 41 which locks thereto and provides at face 42 a seat for the enlarged diameter portion 32 of piston 30.

The diameter of outer sleeve 38 is selected in accord ance with the diameter of piston 30 to define an annular compartment 43 which acts as the fluid storage chamber of the spring. Cooperating with outer sleeve 38 is a lock spring 44 which fits in a circular recess 45 cut completely around the inner wall surface thereof. Behind this look spring is a circular bushing 46 which is held in place by one end of inner sleeve 34. Inner sleeve 34 also has a reduced diameter portion 47, the inner rim portion of which serves as a seat for a helical restoring coil spring 49, the other end of which abuts the free end of piston 30. Inner sleeve 34 is secured in place by a look nut 50 which threads onto its end 37 and prevents this member from moving out of the tubular element 15 during the return stroke of the main piston 6. It will be appreciated that this member cannot move in the opposite direction because of its connection at threaded section 36 with outer sleeve 38 whose wall portion abuts and matches the wall portion of tubular element 15 of the grid structure.

Outer sleeve 38, the main housing of the spring, has several ports, such as 48 and 51, cut through its wall surface at points immediately adjacent the rest location of the increased diameter portion 32 of piston 30. These ports permit a two-way flow of the fluid between the annular compartment 43 and the main body of the radiating assembly. When piston 30 is in the rest position shown, fluid can flow from the main body of the assembly into all of the annular compartments and also into the core of the inner sleeve 34 and piston 30, thus filling these spaces, too.

When piston 6 is accelerated to the right, as seen in this figure, by the force of the slug, not shown, impacting its striking surface 10, the enlarged portion 32 of piston 30 travels with it, compressing the fluid within annular compartment 43. Annular bellows 4, of course, expands at this time to accommodate this piston displacement, thus insuring, as mentioned hereinbefore, the flatness of the peripheral portion of the piston. As piston 30 travels to the right, it quickly reaches a position where its enlarged diameter portion 32 blocks the above ports. When this occurs, equalization of inside and outside pressure is no longer possible, and continued movement of the piston results in additional compression of the fluid within annular compartment 43. Thus, the spring possesses an extremely high degree of stiffness for absorbing a portion of the thrust of the piston. Piston 6 is thus displaced to the right until all of the energy applied thereto is expended. A small portion of this energy, about 4%, is used in compressing the liquid springs. The rest of the energy passes into the liquid surrounding the springs as a compression wave or acoustic pulse. The magnitude of this displacement, of course, depends upon the geometry of the springs, the density of the fluid and the force applied thereto.

During the piston movement, the fluid within the core of inner sleeve 34 and within the hollowed out portion 38 of piston 30 is compressed. This compression is identical with, and augments, the compression of the liquid surrounding the springs. Also, in its movement, piston 6 compresses helical spring 49 a predetermined amount. 7

After the impacting'energy is dissipated, fluid 33 expands and moves piston 30 along with piston 6 black towards its initial or rest position. In order to complete this movement and insure the proper restoration of piston 6, each spring contains, as noted above, a helical spring 49, and these springs act in unison to push each piston to the left until its enlarged portion 32 abuts up against the seat formed by the rear surface of the corresponding tapered nosepiece 41.

As soon as the enlarged portion 32 of each piston opens the ports 48 and 51, fluid pressure is the same both inside space 43 and outside in the fluid surrounding the springs.-

The apparatus is thus prepared for a second cycle of operation.

From What has been described hereinbefore, it will be seen that grid section 2 supports the fluid springs in a manner that allows relatively free passage of the acoustic pulse past-these springs during the positive stroke of piston 6. Hence, the pulse energy radiated from the back surface 11 of piston 6 in response to its displacement cated, as seen in FIG. 1, with a series of three concentric, tapered, conical shells 60, 61 and 62, supported from the main casing 63 by a series of radial members 64, 65 and 66, which members, like radial members 22 and 23, extend substantially the complete length of their section. These radial members are in angular alignment with their counterparts in the grid section which are used to hold the various tubular elements 15, 16, etc., in place. Each of the radial members in the mouth section abuts against a radial member in the grid section, and portions of each conical shell abut the webs in the grid section to further strengthen the overall apparatus. The conical shells, as perhaps best shown in FIGS. 1 and 4, have an appropriate number of recesses, such as 67 and 68, cut

out of their left-hand rim to accept the lock nuts 50 of the various fluid springs. The leading edge 100 of each of these recesses, that is, the portion confronting the rear of the adjacent fluid spring, is tapered to a knife edge to minimize the resistance presented to the acoustic energy emanating from the core of inner sleeve 34 during each positive stroke of piston 6.

Horn mouth section 3, as seen in FIG. 1, is closed off at one end by a disk 70 which is formed with corrugations 71 at a location adjacent its rim portion. This disk, which is made of a material transparent to ,the propagation of acoustic energy and acts as a window, is locked in place by a circular closure ring 72 that is secured to casing 63 by suitable bolts 73.

The three subassemblies, namely, sections 1, 2 and 3, are interconnected by suitable bolts, such as 75 and 76, which pass through aligned holes cut in the flange portions of these units. Once these subassemblies are interconnected, the interior of the radiator can be filled with a fluid, such as eastor oil, which is noncorrosive and has an acoustic impedance near that of salt water, the fluid in which the apparatus is to work. The castor oil can be introduced by means of an aperture 77 cut in the throat section 1 and closed by a plug 78. It would be mentioned at this point that disk 70 should be strong enough to withstand the hydrostatic pressure of the internal fluid when the radiator is out of the fluid medium. To permit this window to accommodate itself to this condition, corrugations 71 are included therein.

Fitting into a circumferential slot 80 formed in section 3 is a deformable, tubular element 81 which is held in place by a band 82. Tubing 81 is in communication with the interior of the radiator by means of a passageway 83 formed in casing 63. This tubing, which is initially filled by a flow of oastor oil from the interior of the radiator, acts as a pressure equalizer to exchange fluid between the exterior and interior of the assembly in accordance with the external environment pressure acting on it. Hence,

for example, as the apparatus is lowered and the pressure on the exterior face of window increased, compensating fluid flows from tubing 81 into the interior to counterbalance this effect. Thus, the pressure on opposite sides of disk 70 remains equal at all times.

A series of three deformable bladders 90, 91 and 92 vent any of the fluid from flowing out of the interior when piston 6 is displaced to the left from the position shown in FIG. 1. This bladder and its companions and 91, by preventing any fluid from occupying the space between adjacent turns of annular bellows 4, reduce the loading on this element and permits it to have a stiffness of the proper degree.

'These bladders, as mentioned hereinbefore, can be filled with either air or nitrogen to a' pressure of, for example, two to five pounds per square inch above atmospheric, which pressure is the same as the castor oil pressure within the main radiator assembly. Suitable valves, such as, for example, those used with automobile tires, can be utilized for the sealing and filling operations.

It would be mentioned that the duration of the acoustic pulse generated by the present apparatus is determined by the geometry of the moving system, that is, the thickness of thepiston and the thickness of the striker impacting it, as well as by the densities of the materials from which these members are fabricated, the density of the castor oil and the velocities of sound propagation in' these materials. It is essentially independent of the spring system and of the maximum pressure determined by velocity of impact.

It would be pointed out in connection with the operation of the pressure-compensating device that storage element 81 has integrally formed therein one or more lines, such as 84, which are accommodated in suitable passageways similar to 83. Container 81, it will be appreciated, is filled via these lines during the filling operation of the main portion of the assembly. Also,

band 82 is perforated throughout its length so as to insure contact between the exterior of tubing 81 and the outside fluid medium.

It would also be pointed out that, although the radiating apparatus is built up of three sections which are practiced otherwise than as specifically described.

What is claimed is:'

1. A radiator assembly for an underwater sound generator comprising, in combination,

-a casing having a circular opening in a pair of opposite ends thereof, said casing including a cylindrical bore section formed therein adjacent one of said circular openings; main piston having a cylindrical body portion, a planar radiating surface, a planar impact surface,

and a circular flange projecting from said cylindrical body portion at a circumferential location adjacent said impact surface, the cylindrical body portion f said piston fitting within said cylindrical bore section and capable of movement therein;

an annular bellows having an inner circular rim and an outer circular rim;

means connecting said inner circular rim of said bellows to said circular flange;

means for connecting the outer circular rim' of said bellows to said casing at one of said circular openings, thereby to close olf that opening;

a diaphragm secured to said casing at said other circular opening and closing off that circular opening;

a grid of interconnectedtubular members of equal diameter retained within said casing with the longitudinal axes of .said tubular elements being perpen-,

dicular to the radiating surface of said piston; a multiplicity of fluid springs, each fluid spring including an enclosed cylindrical chamber,

a piston member having a piston head portion and a piston rod portion connected thereto,

said piston member being accommodated within said cylindrical chamber with the free end of its piston rod projecting through one end wall of said cylindrical chamber,

spring means cooperating with said piston member for normally holding said piston member against one end wall of said cylindrical chamber,

a multiplicity of apertures cut through a wall portion of said cylindrical chamber at a location adjacent said one end wall for permitting a fluid flow into and out of the interior of said chamber;

means for locking each cylindrical chamber of a fluid spring to a tubular element of said grid in an abutting relationship;

a fluid having an acoustic impedance near that of sea water filling said casing and the cylindrical chambers of said fluid springs;

and means connecting the free end of each piston 2. In an arrangement as defined in claim 1,

a deformable gas-filled member disposed between a rim portion of said casing and the inner rim of said annular bellows,

said deformable member preventing the discharge of fluid from the interior of said casing when said main piston vibrates after being struck on its impact surface.

3. In an arrangement as defined in claim 1,

a deformable gas-filled bladder disposed between selected pairs of adjacent turns of said annular bellows thereby to prevent said bellows from being unduly loaded by the surrounding fluid when said casing is disposed within a fluid medium.

In an arrangement as defined in claim 1, a deformable fluid storage member disposed within a recess cut in an outer wall of said casing,

said storage member being exposed to the fluid medium surrounding said casing and adapted to transfer fluid from its interior to the interior of said casing in accordance with the pressure acting on said fluid storage member and the pressure within said casing.

5. In an arrangement as defined in claim 1 wherein said diaphragm has 'a corrugation formed in a portion adjacent its rim which permits the interior portion of said diaphragm to be displaced without distortion when the pressure outside of said casing is less than that within said casing.

No references cited.

LOUIS J. CAPOZI, Primary Examiner. 

1. A RADIATOR ASSEMBLY FOR AN UNDERWATER SOUND GENERATOR COMPRISING, IN COMBINATION, A CASING HAVING A CIRCULAR OPENING IN A PAIR OF OPPOSITE ENDS THEREOF, SAID CASING INCLUDING A CYLINDRICAL BORE SECTION FORMED THREIN ADJACENT ONE OF SAID CIRCULAR OPENINGS; A MAIN PISTON HAVING A CYLINDRICAL BODY PORTION, A PLANAR RADIATING SURFACE, A PLANAR IMPACT SURFACE, AND A CIRCULAR FLANGE PROJECTING FROM SAID CYLINDRICAL BODY PORTION AT A CIRCUMFERENTIAL LOCATION ADJACENT SAID IMPACT SURFACE, THE CYLINDRICAL BODY PORTION OF SAID PISTON FITTING WITHIN SAID CYLINDRICAL BORE SECTION AND CAPABLE OF MOVEMENT THEREIN; AN ANNULAR BELLOWS HAVING AN INNER CIRCULAR RIM AND AN OUTER CIRCULAR RIM; MEANS CONNECTING SAID INNER CIRCULAR RIM OF SAID BELLOWS TO SAID CIRCULAR FLANGE; MEANS FOR CONNECTING THE OUTER CIRCULAR RIM OF SAID BELLOWS TO SAID CASING AT ONE OF SAID CIRCULAR OPENINGS, THEREBY TO CLOSE OFF THAT OPENING; A DIAPHRAGM SECURED TO SAID CASING AT SAID OTHER CIRCULAR OPENING AND CLOSING OFF THAT CIRCULAR OPENING; A GRID OF INTERCONNECTED TUBULAR MEMBERS OF EQUAL DIAMETER RETAINED WITHIN SAID CASING WITH THE LONGITUDINAL AXES OF SAID TUBULAR ELEMENTS BEING PERPENDICULAR TO THE RADIATING SURFACE OF SAID PISTON; A MULTIPLICITY OF FLUID SPRINGS, EACH FLUID SPRING INCLUDING AN ENCLOSED CYLINDRICAL CHAMBER, A PISTON MEMBER HAVING A PISTON HEAD PORTION AND A PISTON ROD PORTION CONNECTED THERETO, SAID PISTON MEMBER BEING ACCOMMODATED WITHIN SAID CYLINDRICAL CHAMBER WITH THE FREE END OF ITS PISTON ROD PROJECTING THROUGH ONE END WALL OF SAID CYLINDRICAL CHAMBER, SPRING MEANS COOPERATING WITH SAID PISTON MEMBER FOR NORMALLY HOLDING SAID PISTON MEMBER AGAINST ONE END WALL OF SAID CYLINDRICAL CHAMBER, A MULTIPLICITY OF APERTURES CUT THROUGH A WALL PORTION OF SAID CYLINDRICAL CHAMBER AT A LOCATION ADJACENT SAID ONE END WALL FOR PERMITTING A FLUID FLOW INTO AND OUT OF THE INTERIOR OF SAID CHAMBER; MEANS FOR LOCKING EACH CYLINDRICAL CHAMBER OF A FLUID SPRING TO A TUBULAR ELEMENT OF SAID GRID IN AN ABUTTING RELATIONSHIP; A FLUID HAVING AN ACOUSTIC IMPEDANCE NEAR THAT OF SEA WATER FILLING SAID CASING AND THE CYLINDRICAL CHAMBERS OF SAID FLUID SPRINGS; AND MEANS CONNECTING THE FREE END OF EACH PISTON MEMBER OF SAID FLUID SPRINGS TO SAID MAIN PISTON AT DIFFERENT POINTS ABOUT ITS RADIATING SURFACE WHEREBY, WHENEVER A FORCE IS APPLIED TO THE IMPACT SURFACE OF SAID MAIN PISTON AND SAID MAIN PISTON DISPLACED WITHIN SAID CYLINDRICAL BORE SECTION, SAID PISTON MEMBERS OF SAID FLUID SPRINGS MOVE WITHIN SAID CYLINDRICAL MEMBERS TO FIRST FORCE SOME OF THE FLUID WITHIN SAID CHAMBERS OUT THROUGH SAID APERTURES INTO THE INTERIOR OF SAID CASING AND THEN COMPRESS THE REMAINING FLUID LEFT WITHIN SAID CYLINDRICAL CHAMBERS. 